Green MP Holly Walker is to step aside at this election, citing family reasons.

Ms Walker is candidate for Hutt South – currently held by Labour’s Trevor Mallard, who won the seat at the 2011 election with slightly fewer than 16,000 votes. She was - until today - ranked 12 on the Green Party list for this election.

Ms Walker garnered 3693 votes and says she will still campaign for the Green Party vote in the electorate.

National is making a strong play for the seat, having won the party vote there in 2011 although the then National candidate, Paul Quinn, was behind Mr Mallard by nearly 4000 votes.

New candidate Christopher Bishop, who previously worked for cabinet minster Gerry Brownlee, is already highly active in the electorate.

Mr Bishop knows Ms Walker of old: this afternoon he commented on Twitter they “have been mates since uni days – once kipped on her floor at Oxford for 2 nights in 07.”

What happens to Ms Walker’s votes could make the difference between Mr Mallard hanging on to the seat – which he has held, in different forms, since 1993 – or not. It will be the toughest challenge the controversial Labour veteran has had in what was once a safe Labour seat.

On paper at least, today’s announcement helps Mr Mallard, though not by a great margin.